1. Field of the Invention
The present invention relates to a luminescent lamp, and more particularly, to a flat luminescent lamp and a method for manufacturing the same.
2. Discussion of the Related Art
Ultra thin flat panel display devices, especially liquid crystal display (LCD) devices, are widely used in monitors for notebook computers, spacecrafts, and aircrafts.
A passive luminescence LCD device usually includes a back light provided at the rear of a liquid crystal panel and used as a light source. The back light is inefficient because it increases the weight, power consumption, and thickness of the device.
The back light used as a light source of an LCD is formed in such a manner that a cylindrical fluorescent lamp is often used. There are two types of back light: a direct type and a light-guiding plate type.
In the direct type back light, a fluorescent lamp is mounted on a flat panel. To avoid having the shape of the fluorescent lamp displayed on a liquid crystal panel, it is necessary to maintain the distance between the fluorescent lamp and the liquid crystal panel and arrange a light-scattering means to achieve a uniform light distribution. As a result, it is difficult to form a LCD back light with a very thin size.
As the panel size gets larger, a light-emitting area of the back light increases. If the direct type back light has to cover a large area, the light-scattering means has to have a sufficient thickness to make the light-emitting area flat. This also makes it difficult to form a thin sized back light for LCD devices.
For the light-guiding plate type back light, a fluorescent lamp is mounted outside a flat panel so that light is dispersed in all sides using a light-guiding plate. In this case, since the fluorescent lamp is mounted at one side and light passes through the light-guiding plate, luminance becomes too low. Also, for uniform distribution of luminous intensity, advanced optical design and processing technologies are required.
Currently, to achieve high luminance, a direct type back light has been proposed in which a number of lamps are arranged below a display surface. Alternatively, a lamp with a bent shape is proposed. Recently, a flat luminescent back light with a flat surface facing a display surface of a panel is being researched and developed. This flat luminescent back light is disclosed in U.S. Pat. No. 6,034,470.
A related art flat luminescent lamp will be described with reference to the accompanying drawings.
FIG. 1 is a plane view illustrating a related art flat luminescent lamp, and FIG. 2 is a sectional view taken along line I-I′ of FIG. 1.
As shown in FIGS. 1 and 2, the related art flat luminescent lamp includes a lower substrate 11, an upper substrate 11a, cathodes 13 formed on the lower substrate 11, anodes 13a formed on the upper substrate 11a, four frames 19a, 19b, 19c, and 19d for sealing the lower and upper substrates 11a and 11 by a glass solder, and a plurality of support rods 21 formed between the lower and upper substrates 11 and 11a. 
The anodes 13a are formed in pairs at constant intervals. The cathodes 13 are formed on the corresponding lower substrate 11 between the anodes 13a The cathodes 13 and the anodes 13a are coated with a dielectric material, and an external voltage is applied to the cathodes 13 and the anodes 13a through a lead line.
A surface of the upper and lower substrates 11a and 11 facing a discharge space is coated with a fluorescent material. In the discharge space, a Xe gas induces discharge, forms plasma and emits ultraviolet rays (UV). The emitted UV comes into collision with the fluorescent material formed on the upper and lower substrates 11a and 11. For this reason, the UV is excited to generate visible rays.
Additionally, a reflecting plate 14 is further provided on the lower substrate 11. The reflecting plate 14 serves to prevent the visible rays generated in the discharge space from leaking out to the rear of the lower substrate 11. The support rods 21 are made of a glass material so as not to interrupt emission of the visible rays.
Meanwhile, referring to FIG. 2, the cathodes 13 are formed on the lower substrate 11 of glass material, and a first dielectric material layer 12 is formed on the lower substrate 11 including the cathodes 13. The reflecting plate 14 is formed on the first dielectric material layer 12 and a first phosphor layer 15 is formed on the reflecting plate 14. The anodes 13a that induce discharge together with the cathodes 13 are formed on the upper substrate 11a of glass material. A second dielectric material layer 12a is formed on the upper substrate 11a including the anodes 13a. A second phosphor layer 15a is formed on the second dielectric material layer 12a. On the upper and lower substrates 11a and 11, frames 19a, 19b, 19c, and 19d are formed to seal the upper and lower substrates 11a and 11 by a glass solder.
The cathodes 13 and the anodes 13a are formed by a silk printing or vapor deposition process.
In the aforementioned related art flat luminescent lamp, if the voltage is applied to the cathodes 13 and the anodes 13a through the lead line, the Xe gas forms plasma in the discharge space between the cathodes 13 and the anodes 13a and emits UV. At this time, the UV comes into collision with the first and second phosphor layers 15 and 15a to generate visible rays.
However, the related art flat luminescent lamp has several problems. Since four frames and a number of the support rods are required to seal the lower and upper substrates, the number of parts for manufacturing the lamp increases and the process steps become complicated. This also leads to the increased weight and volume of the lamp.